1. The Field of the Art.
The present invention relates to a device for controlling the temperature of an enclosed area at a predetermined temperature, and, more specifically, to the use of a thin film resistor made of a superconducting material that acts as both temperature sensor and a heater.
2. Description of the Prior Art.
Many different types of temperature controllers are known. For low temperature applications that use a heat sink, a detector usually measures the temperature for the area of interest. The output of the detector is then input, through conversion circuitry, to a heating element that maintains the temperature of the area within a certain range. The use of a separate detector and heating element requires this conversion circuitry, which can add cost and decrease sensitivity.
A controller is known that incorporates the sensing element and the heating element into a single device. U.S. Pat. No. 3,155,157 uses a resistive bridge circuit that senses the temperature and also serves as a heating element within an enclosed area. However, the sensitivity of the bridge circuit is rather low and difficult to maintain. Furthermore, conversion circuitry that detects and A.C. error nulling signal is also required.
Thus, a temperature controller that does not contain conversion circuitry and has an element that acts as both a temperature sensor and a heating element is needed.